Recently, an audio system has been increasing number of audio channels in a single audio source for more realistic sound. Also, a speaker/earphone and so on have been continuously appearing for each audio reproduction by the generalization of new and diverse digital media and the advent of various kinds of terminal units that are suitable therefore.
As a scheme that can establish a single audio reproduction system in the home by integrating various kinds of terminal units, there is a scheme using a conventional audio receiver. The audio receiver receives each audio signal from various kinds of audio sources such as TV, CD player, DVD player, MP3 player, FM/AM tuner, cassette player, etc., and amplifies one of the audio signals selected by a user and outputs it to one or more speakers.
As mentioned above, the audio system has an increased number of audio channels from one audio source, like 4.1, 5.1, 6.1 and 7.1 channels, etc., beyond the past simple stereo system for more realistic sound, and at the same time has an increased number of speakers that are required for each channel. Thus, there exist wiring and arrangement problems in the home due to the increased number of speakers.
Hence, in the audio system having multi channel speakers, each speaker is connected to one amp or an A/V receiver incorporating an amp therein by wire or wireless. That is, the audio system employs a wired method since its wiring arrangement is relatively easy in case of front speakers, and a wireless method in case of rear/satellite speakers. This leads to the advent of products that facilitates the arrangement of speakers.
Among these products, there are products having the form of wireless headphone, not speaker. A transmitter having the form of a wireless headphone holder converts an output signal of an audio receiver into a wireless (RF or IR) signal and then transmits it to the wireless headphone. However, these products converts all input audio signals into analog signals and thereafter sends the analog signals using a radio frequency (RF) or an infrared rays (IR). Therefore, there may be a bad change in the quality of received signals by distance/directivity/obstacle between the transmitter and the receiver, which results in the degradation in quality of reproduced audio signals.
Further, the products also convert digital audio sources into analog signals and then transmit them, and thus, the quality of digital audio source in the audio source is not maintained in that state until the reproduction time thereof.
In addition, since the products are configured to always have pairs of transmitters and speakers (or headphones), no interlinking is made between heterogeneous products, hence the total number of speakers (or headphones) in the home cannot be reduced.
To solve the above-mentioned problems, there has been proposed a scheme that transmits and receives audio signals through a network using a wired network like Ethernet or PLC (Power Line Communication) based on the concept that the input of power is essential in all speaker output units.
However, since the wired network or PLC requires an IP-based network, its protocol is relatively complicated and there exists a difficulty in IP management as the number of units increases. Moreover, the wired network or PLC has a drawback that it cannot guarantee a desired quality of traffic if the traffic increases.
Further, the PLC scheme has a burden on an additional installment cost for configuration of initial PLC network that inherently has, and also a relatively small transmission bandwidth. In result, it is difficult to select such a PLC scheme.
Moreover, the PLC scheme requires a process of connecting a portable device to a power line or it thereto via a separate unit for connection with the portable device, thereby limiting mobility of the portable device.
Consequently, there is a need for improvement in the conventional audio system that it facilitates the arrangement and wiring of various speakers and maintains the original quality of audio signals, and various stationary and portable audio reproduction devices can reproduce audio signals freely through speakers already installed therein.